In one of the most important constitutional cases in generations, three senior judges ruled that the Prime Minister does not have power to use the royal prerogative to trigger Article 50 of the Lisbon Treaty to start the two-year process of negotiating Brexit without the authority of Parliament.

In a speech given in Malaysia on the evolving constitutional role of the UK Supreme Court, Lady Hale said: “Just before I left to come here, a unanimous divisional court held that the Secretary of State does not have power under the royal prerogative to give notice to withdraw from the European Union.

She added: “As is well known, the referendum on whether the United Kingdom should leave or remain in the European Union produced a majority of 51.8 per cent in favour of leaving. But that referendum was not legally binding on Parliament.”